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SubjectRe: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm2-V0.7.30-2

On Wed, 1 Dec 2004, Ingo Molnar wrote:

>
> * Paul Davis <paul@linuxaudiosystems.com> wrote:
>
> > >also, the problem is that jackd uses _named_ fifos, which are tied to
> > >the raw FS and might trigger journalling activities. Normal pipes
> > >(unnamed fifos) would not cause such problems. Would it be possible to
> > >change jackd to use a pair of pipes, instead of a fifo?
> >
> > i.e. pipe(2) rather than mkfifo(2) ?
> >
> > it would be a complete pain because the pipes have to be
> > "discoverable" across processes. we would have to do fd passing, which
> > is still really quite ugly in linux (and other *nix systems). it would
> > quite difficult, though not impossible.
>
> yeah. And i think mkfifo(2) objects ought to behave atomically as well,
> it's an unfortunate side-effect of atime/mtime inode semantics that they
> can block.
>
> your point is correct, the best way to have a system-wide namespace for
> synchronization objects is ... the filesystem hierarchy. If you create a
> unix domain socket then you can distribute your pipe fds, but that's
> indeed somewhat painful.
>

Don't worry about setting up the stuff. Once you have the pipe it ought to
be RT in the usage of read/write, but setting it up is something you is
something you do "under boot", just as allocating memory and other
non-real-time stuff.


> Ingo
>

Esben

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